2. Background  The soft shell clam, Mya arenaria, currently occupies a large geographical range in the northern hemisphere.  Soft shell clams are found on the European coast from northern Norway to Portugal.  Mya arenaria, or “steamer clam” is a commercially important bivalve in North America, and has the potential to be an exploited species in European waters in the future.

3. Mya arenaria in the Irish Sea  This project is part of a larger funded study (SUSFISH) which is researching shellfish management in the Irish Sea.  Soft shell clams are present in the Irish Sea, but little information is currently available on their biology and distribution.  The SUSFISH study aims to assess the potential threat of climate change to the shellfish industry in the Irish Sea.

4. Objectives of Research  Investigate the biology, including the reproductive cycle, of M. arenaria in the Irish Sea.  To look at the health status of softshell clams and to identify any pathogens.  To study the population genetics of Irish Sea soft shell clams and to see how they compare with elsewhere in the distributional range.  To integrate the data collected on the biology of M. arenaria into future climate change predictions.

5. Methodology  Thirty soft-shell clams are collected every month from Bannow Bay, Co. Wexford, Ireland, from March 2010 to June 2011.  Bannow Bay is located in the Irish Sea, on the southeast coast of Ireland (52°13’33 N, 6°47’51 W).  General biology, spawning and gametogenic patterns of Mya samples are being investigated.  Each individual is screened for parasites and disease.

6. Molecular Ecology Methods  Strasser and Barber (2009) used “universal" DNA primers to amplify the variable mitochondrial cytochrome oxidase I gene (COI).  Gill samples of Irish Sea M. arenaria are being sequenced and findings compared to past results.  Generic primers are used to amplify  Bacterial DNA (Ji et al, 2010)  Ostreid Herpes Virus (Renault & Arzul, 2001)  DNA samples are also being sequenced to detect the presence of pathogens.

7. Results - Sex Ratio  432 Mya arenaria have been collected over 16 months from March 2010 to June 2011.  199 (46%) were female and 229 (53%) were male.  4 (1%) were immature or the sex could not be determined.  The overall female:male sex ratio of 1:1.15 did not show a significant divergence from a 50:50 ratio ( χ 2 test – NS).  No hermaphrodites were present in the collected samples, and there was no evidence of protandry.

8. Results – General Biology  Average weight of all M. arenaria collected was 74g (+/-4.9g).  Average length of all individuals was 8.2 cm (+/-0.2cm).  Female individuals were both lighter and shorter than male M. arenaria, though this was not statistically significant.

9. Results – Gonadal Development Female M. arenaria (20X magnification) Indeterminate Developing Ripe Spawning Spent Male M. arenaria (20X magnification)

10. Results – Reproductive Cycle  Of the collected samples, male M. arenaria were developing from March to July 2010, with ripe individuals present from May. Spawning began in August and was completed by November 2010.  The female M. arenaria show a less defined cycle, but most individuals collected were ripe or spawning in August and September 2010.

11. Results – Reproductive Cycle  In 2010, M. arenaria matured over the summer months, with both sexes either ripe or spawning by August.  Spawning was in a single spawning episode and was completed by November.  Gametogenic development appears to have been affected by an unusually cold winter, so completion of spawning may be slightly late in 2011.  The mean temperature at Bannow Bay was highest in June, at 18°C and lowered to 3°C by December 2010.

12. Results - Disease  Histological methods have not identified the presence of any pathogens to date.  PCR amplification and subsequent sequencing of M. arenaria gill samples using Ostreid Herpes Virus and generic bacterial DNA primers have shown no presence of pathogens.

13. Results – Molecular Ecology ~ 100 bp ~ 650 bp  At present, no genetic variation has been evident in Irish Sea samples at the variable CO1 site.  Sequencing of Irish Sea Mya arenaria have revealed the common haplotype described by Strasser & Barber (2009) at this site.

14. Summary  This study is the first to assemble information on Mya arenaria in Ireland.  Data gathered indicates the presence of a sustainable, healthy population.  Due to softshell clams ability to survive and reproduce in such a variety of differing areas, and the lack of disease compared to American stocks, it could be an ideal species to culture in European waters in the future.  The data collected here could inform development of a potential fishery.  By continuing to gather this type of information we can develop a sustainable fishery that could support local communities.

15. Acknowledgements This project was funded by the Ireland Wales Programme 2007-2013 INTERREG 4A European Regional Development Fund (ERDF).